1. Field of the Invention
The invention generally relates to doors, and more particularly, to door systems which can be selectively actuated and reset to a normal operational mode.
2. Description of the Related Art
Modern building practices include a wide array of measures aimed at fire prevention and control. Besides alarm systems, buildings are commonly equipped with additional fire prevention and control measures, such as sprinkler systems and portable fire extinguishers. In addition, many structures are equipped with safety systems, including fire doors, to inhibit the spread of fire beyond a particular area. Typically, a fire door is configured to remain open until a particular triggering event, such as the presence of abnormal heat or smoke, causes the door to close. After the door closes, the fire, as well as smoke, fumes, and heat, tend to be contained on one side of the door.
For example, referring to FIG. 1, a conventional safety system in the form of a fire door system 20 is configured to prevent the spread of smoke, flames, heat, or other substances from one area to another area. In the fire door system 20, a fire and smoke resistant curtain 22 is adapted to be raised or lowered to open or close a passage, such as a hallway, door, window, or the like. The curtain 22 is guided by tracks 24 located on either side of the curtain 22 and attached at one end to a barrel 26. The barrel 26 is fixed to an axle 28 that is supported for rotational movement between a pair of end plates 30. As the axle 28 is rotated in a first direction, the curtain 22 rolls off the barrel 26 and the passage is closed. Conversely, as the axle 28 is rotated in a second direction that is opposite to the first direction, the curtain 22 rolls onto the barrel 26 and retracts inside of a hood 32 such that the passage is opened.
When the curtain 22 is rolled onto the barrel 26 in order to provide an unobstructed passage, it is normally biased by gravity to roll off the barrel 26 and close the passage. Therefore, a tension spring 34 is disposed about the axle 28 and suitably wound so as to counterbalance the tendency of the curtain 22 to fall. However, once a triggering event occurs that dictates that the curtain 22 should be lowered (e.g., a fire), the counterbalancing force provided by the tension spring 34 is released so that the curtain 22 unwinds from the barrel 26 and closes the passage.
To accomplish this releasing function, a first release device 36 is attached to a retention mechanism (not shown) which engages one end of the tension spring 34. Disengaging the retention mechanism releases the tension on the tension spring 34, and thus the counter-balancing force applied to the axle 28. In addition, a second release device 35 can be attached to the opposite end of the first release device 36. The second release device 35 is connected to one end of the first release device 36 such that the first release device 36 engages the tension spring 34 until an alarm is received or in some instances, until a power outage occurs. If an alarm is received or a power outage is encountered, the second release device 35 will release the one end of the first release device 36 such that the retention mechanism is disengaged. Alternatively, if the first release device 36 melts due to heat generated by a fire or an explosion, the retention mechanism releases one end of the tension spring 34, allowing the tension spring 34 to unwind. This allows the axle 28 to rotate such that the curtain 22 rolls off the barrel 26 and lowers to close the passage. However, if the second release device 35 receives a false alarm signal (or in some instances, an intermittent power interruption occurs), the door may inadvertently close during non-emergency periods.
Due to the important function provided by fire door systems 20, they are frequently tested to ensure that the system 20 properly functions. Testing typically includes activating the first release device 36 such that the tension spring 34 is released and the curtain 22 lowers to a closed position. After the test is completed, however, the curtain 22 is raised and the tension spring 34 readjusted to maintain the curtain 22 in the opened position. Because the tension spring 34 adjustment is crucial to the system 20 operation, a special technician usually resets the door. Therefore, maintenance of the fire door system becomes labor intensive and expensive.